Apparatus for degassing molten metal



Aug. 31, 1965 P. J. WOODING ETAL 3,203,685

APPARATUS FOR DEGASSING' MQLTEN METAL Filed May 16. 1961 3 Sheets-Sheet 2 IN VEN TORS.

arrow/5y Aug. 31, 1965 P. J. WOODING ETAL 3,203,686

APPARATUS FOR DEGASSING MOLTEN METAL 3 Sheets-Sheet 3 Filed May 16. 1961 I N VEN TORS.

z/QTTOR/VEY United States Patent 3,203,686 APPARATUS FOR DEGA'SSING MOLTEN METAL Patrick J. Wooding, Canonsburg, Peter J. Wynne, Pittsburgh, and Walter 'Sieckman, 'Canonsburg, Pa., assignors to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed May '16, 1961, Ser. No. 110,462 Claims. (Cl. 266-3'4) This invention relates to apparatus for the vacuum degassing of molten metals and, more particularly, to apparatus for adding alloying or refining compounds to the melt during degasification.

The production of certain steel alloys requires the reduction of oxygen, carbon and hydrogen. Because chemical reactions involving these elements have a gas phase and can be made to occur at reduced pressures, their removal can be accomplished expeditiously by treating the melt in a vacuum chamber.

The type of vacuum degassing apparatus used to illustrate the preferred embodiment of the instant invention, is one wherein a vacuum chamber is disposed above a ladle of molten metal and the two are arranged for relative movement toward and away from each other. A

nozzle extends downwardly from the lower end of the vacuum chamber so that upon movement of the chamber and the ladle toward each other, the reduced pressure in the chamber draws molten metal through the nozzle whereupon degasification takes place due to the action of the vacuum therewith. Upon relative movement of the chamber and ladle away from each other, molten metal discharges through the nozzle to intermix with the remaining metal within the ladle. If desired, a new portion of the melt may be redrawn into the chamber by again relatively moving the vessel and ladle toward each other. This process is repeated until the desired degree of total degasification has been achieved.

During the degasification of certain alloys, it may become necessary to add certain alloying or refining com pounds to the melt. For example, in the production of heavy forgings, difficulties have been experienced due to oxide inclusions. Significant quantities of oxygen, however, can be removed rapidly only when it is in an uncombined form. Therefore, it is essential to degas the melt prior to the addition of elements, such as silicon, which have a high oxygen aflinity. By making such additions late in the degassing cycle, it is possible first to remove most of the free oxygen in the form of a gaseous deoxidation product such as carbon monoxide. Due to the configuration of the degassing apparatus, additions can most conveniently be made through the vacuum chamber. The addition of additives during degasification also has the advantage of increased speed in that the intermixing of the melt, inherent in the above described degasification process, eliminates the necessity for an additional mixing procedure. However, because the hopper used to insert such additives into the vacuum chamber must be a part of the over-all sealed system, no additional material can be placed in the hopper once the degassing operation has commenced. Hence, charging of the hopper must be completed prior to the disposition of the ladle containing the molten metal below the degassing chamber.

It will be appreciated, too, that in order to obtain the specified alloy grades, it is necessary that the unit weight of additives per ton of melt be held within close tolerances. This is complicated by the fact that it is extremely difiicult to accurately predetermine the exact yield of any given melting furnace.

It is an object of the invention to provide a hopper for charging the melt in a vacuum degassing chamber with additives during a degassing operation.

Patented Aug. 31, 1965 A further object of the invention is to provide means for adding alloying or refining compounds to the melt in a vacuum degassing chamber from a sealed hopper wherein the weight of the material added can be varied after the hopper has been sealed so that the amount of such additives can be controlled relative to the weight of melt being degassed.

These and other objects and advantages of the invention will become more apparent from the detailed description of the preferred embodiment of the instant invention taken with the accompanying drawings in which:

FIG. 1 is a side elevational view, partly in section, of vacuum degassing apparatus incorporating the instant invention;

FIG. 2 is a perspective view of a hopper according to the instant invention; 7

FIG. 3 is a top view of the hopper shown in FIG. 2; and

FIG. 4 shows the release mechanism used with the instant invention.

In general terms, the invention comprises a hermetically sealed receptacle for use with a vacuum degassing vessel and which includes a main compartment and a plurality of smaller auxiliary compartments which are volumetrically inter-related according to a geometric progression which increase by a factor of two, and means external of the hopper for individually discharging the contents of each auxiliary compartment into the main compartment.

Referring now to the drawings in greater detail, FIG. 1 shows vacuum degassing apparatus comprising a vessel 10, a ladle 11 containing molten metal 12 and a lifting mechanism 14 for supporting the vacuum chamber and for moving it vertically relative to the ladle 11. The degassing vessel 10 includes a steel shell 15 which encloses an inner refractory lining 16. A layer of heat insulating material 18 is disposed between the metallic shell 15 and the refractory lining 16, to minimize heat radiation losses from the vessel 10. The steel shell 15 provides a support for, and hermetically seals the chamber 23 defined by the relatively porous refractory lining 16.

A nozzle 20 is affixed to the lower end of vessel 10 and has a cylindrical bore 22 that communicates with the chamber 23 defined by the refractory lining 16. It will be noted that the lower end of the nozzle 20' which extends below the surface of the melt 12 during a degassing operation is also provided with refractory material at its outer surface to prevent contact between the metallic shell 15 with the molten metal 12.

An evacuating apparatus 24 is connected to the chamber 23 of vessel 10 by a conduit 26 which is connected in a hermetically sealed relation to the shell 15 adjacent an aperture 28 in the roof 29 of refractory lining 16. A car 30 movably mounted on rails 32 below vessel 10' is provided to support and position the ladle 11. The lifting mechanism 14 includes a platform 34 upon which the vessel 10 vertically. Control of the hydraulic rams is draulic rams 36 for moving the platform 34 and the vessel 10 vertically. Control of the hydraulic rams is effected by an operator stationed at a remote location. While in the preferred embodiment of the invention the vessel 10 is shown to be vertically movable, it will be appreciated that the device would operate equally as well if the vessel 10 were stationary and the ladle 11 movable.

Operation of the vacuum degassing apparatus will now be described. After the ladle -11 of molten steel 12 has been positioned below the vessel 10, the latter is lowered until the nozzle 20 extends a predetermined distance below the surface of the melt 12. The evacuating apparatus 24 is then activated to produce a partial vacuum within the chamber 23. As a result of the difference in pressure between the interior of chamber 23 and the atmospheric pressure acting on the surface of the melt 12, a portion of said melt, identified by the reference numeral 12' to distinguish it from the main body of the melt 12, is forced upward through nozzle 20 and into chamber 23 where gases dissolved therein are drawn off by the operation of the partial vacuum. After this portion 12 of the melt 12 has been degassed for a predetermined length of time, the vessel is raised thereby causing the melt 12' to discharge into the ladle 11 to produce a vigorous stirring with the remainder of the melt 12. The lower end of the nozzle 20, however, remains below the surface of the melt 12 to maintain the partial vacuum within chamber 23. This process may then be repeated, -by successively lowering and raising vessel 10, until the desired degree of total degasification has been achieved.

A hopper 38, for charging chamber 23 with refining or alloying additives, is mounted atop steel shell by means of a flange 39 which is afiixed to a cooperating flange 40 atop a short pipe 41 integral with and passing through the steel shell 15. An opening 42 in the roof 29 of lining 16 adjacent the lower end of pipe 41 places the hopper 38 in communication with the interior of vessel 10. An externally controlled valve 43 is operative to discharge the contents of hopper 38 into chamber 23.

Referring now specifically to FIGS. 2 and 3, the hopper 38 is shown to have a main body 44 and a cover 45. The body portion 44 has the general shape of a truncated oblique cone whose lower end terminates in the flange 39 and whose upper end terminates in a short cylindrical section 53. At the upper end of section 53 an inwardly extending flange 46 is provided and has an annular groove 47 for receiving a gasket 48. In addition, a plurality of tapped holes 49 are formed around the flange 46 in spaced relation relative to each other and radially outwardly from the gasket 48. Similarly a rim 50 is formed in the underside of cover 45 for cooperatively engaging the flange 46 and has a plurality of apertures in registry with holes 49 when the cover 45 is closed so that the cover may be secured to the body portion 44 by bolts 52. In this manner the hopper 38 is hermetically sealed. It will be appreciated from the foregoing that once the hopper 38 has been sealed additional material cannot be laced therein without breaking its seal, which would then destroy the vacuum within chamber '23.

The main body portion 44 of hopper 38 .is divided into a main compartment 54 and three auxiliary or trimming compartments 55, 55a and 55b. More specifically, a plurality of vertical divider panels 58 are disposed in the upper end of body portion 44 and extend radially from the axis of the cylindrical upper portion 53 outwardly to the side of said body portion. In addition, a support panel 60 extends from the intersection of the divider panels 58 to the opposite side of the cylindrical upper portion 53. A pie-shaped floor panel 62 is provided for each of the trimming compartments and each extends downwardly from the inner edge of the flange 46 toward the interior of the body portion 44 and each is afiixed at its sides to the lower ends of its associated divider panels 58. As seen in FIG. 2, each of the floor panels 62 slants downwardly toward the center of body portion 44 to facilitate the discharge of additives from the auxiliary compartments 55, 55a and 55b into the main compartment 54. Also, as seen more clearly in FIG. 3, each Of the bottom panels 62 terminates at a point a short distance from the junction of the divider panels 58 to create an opening in the lower end of each of the compartments 55, 55a and 55b. These openings are closed by gates or doors 64, 64a and 64b respectively which may be individually operated by a corresponding control mechanism 65, 65a or 65b in a manner to be described hereinbelow.

In order to obtain the desired volume of additives, the compartments 55, 55a and 55b are volumetrically interrelated according to a geometric progression which increases by a factor of two. In other words, compartment 55 has a volume twice as large as compartment 55a and compartment 55a has a volume twice as large as compartment 55b. Therefore, if the volume of compartment 55b is considered as being unity, then the volumes of compartments 55a and 55 will be two and four respectively. Thus, by a proper combination of the additives in the compartments 55, 55a and 55b, additive volumes of one, two, three, four, five, six or seven times unity may be obtained, in addition to the additive in the main compartment 54.

This will be more readily understood from the following example. Assume that the weight of melt 12 in a series of ladles 11 to be degassed can range from 160 to 195 tons. The main compartment 54 of hopper 38 is filled with sufficient additive to accommodate 160 tons melt and the trimming compartments 55, 55a and 55b are filled with four, two and one units of additives respectively, wherein each unit is sufiicient for 5 tons of melt. Hopper 38 is then sealed in preparation for a degassing operation. If, for example, a yield of 175 tons of melt is obtained from the first furnace, the operating means 65a and 65b will be actuated to open gates 64a and 64b and thereby discharge three units of material from the trimming compartments 55a and 55b into the main compartment 54 so that there will be sufficient additives therein to accommodate 175 tons of melt. If the weight of melt 12 in ladle 11 were at the lower limit of 160 tons, then the additives within the main compartment '54 would be sufficient and, therefore, those within trimming compartment 55, 55a and 5512 would not be used. Conversely, if the maximum weight of 195 tons were reached, then the additives within each of the trimming compartments would be utilized. Any weight of melt between and tons would be similarly accommodated by a proper combination of the contents of the various trimming compartments.

Each of the operating mechanisms 65, 65a and 65b is identical and, accordingly, for the sake of brevity, only 65 will be explained in detail in conjunction with FIG. 4. It can be seen that the gate 64 is afiixed to shaft 66 which extends horizontally through a packing gland 68 aflixed to the wall of the body portion 44 of hopper 38 and which s substantially parallel to one of the divider panels definmg the compartment 55. A mounting plate 69 is affixed to a flange 70 on the outer end of the packing gland 68 and supports an air cylinder 72 and a latching assembly 73 of the operating mechanism 65. The latching assembly 73 includes a latch arm 74 which is keyed to shaft 66 and which is held in horizontal or latched position, as shown in FIG. 4, by a latch 75. Latch 75 is pivotally mounted at 77 between a pair of support arms 78 aflixed to a plate 79 which defines one end of the air cylinder 72.

A piston 80 is disposed within air cylinder 72 and is pivotally connected to the latch 75 by a rod 81 which engages said latch between its pivotal mounting 77 and ts other end 76. A spring 82 surrounds the rod 81 and is disposed between piston 80 and the plate 79 thereby urg ng said piston to the right, as viewed in FIG. 4, and against a stop sleeve 83. This holds the latch 75 in its latched position relative to the arm 74 and, hence, the gate 64 in horizontal or closed position. The righthand end of air cylinder 72 is connected by a conduit 84 to an an supply through coupling 85. When it is desired to discharge the contents of trimming compartment 55 into the main compartment 54, high pressure air is supplied to the righthand end of air cylinder 72 forcing piston 80 to the left against the action of spring 82. As a result, the latch 75 is pivoted in a counterclockwise direction to release latch arms 74 whereupon gate 64 will pivot in a clockwise direction due to the weight of the additive thereon as well as its own weight thereby discharging the contents of compartment 55 into the main compartment 54. The contents of the main compartment 54 will then be correct relative to the weight of melt 12 in ladle 11 and will subsequently be discharged into the chamber 23 after the degassing operation has proceeded for a predetermined time. A handle 86 is provided on the end of latch arm 75 so that it may be rotated to its horizontal position and relatched upon the release of the air in the cylinder 72 so that the operating mechanism 65 may be reset for a subsequent operation.

While only a single embodiment of the invention has been shown and described and while the invention has been discussed in relation to a particular vacuum degassing apparatus, it is intended that the scope of the invention be limited only by the appended claims.

We claim:

1. In combination, a sealed vessel for the vacuum treatment of molten metal, and hermetically sealed receptacle means mounted adjacent said vessel and interconnected thereto, said receptacle means being divided into a plurality of compartments comprising a main compartment and a plurality of auxiliary compartments, said auxiliary compartments being volumetrically inter-related according to a geometric progression which increases by a factor of two first means for individually discharging the contents of said auxiliary compartments into said main compartment and second means for discharging the contents of said main compartment into said vessel.

2. A vacuum vessel for vacuum treating a ladle of molten metal, a hermetically sealed receptacle mounted on said vessel and connected to the interior thereof, said receptacle having a main compartment and a plurality of auxiliary compartments, each of said auxiliary compartments having a predetermined different volume which is interrelated according to a geometric progression, and means for individually discharging predetermined ones of said auxiliary compartments into said main compartment so that the quantity of material fed into said vessel can be regulated after the commencement of a degassing operation Without unsealing said vessel.

3. A sealed vessel for the vacuum treatment of molten metal, said vessel having a metallic shell and a refractory lining, a hermetically sealed receptacle mounted adjacent said vessel for feeding material into said vessel, means dividing said receptacle into a main compartment and a plurality of auxiliary compartments, said auxiliary compartments being volumetrically inter-related according to a geometric progression which increases by a factor of two, and means for selectively discharging predetermined ones of said auxiliary compartments into said main compartment.

4. A sealed vessel for the vacuum treatment of molten metal, said vessel having a metallic shell and a refractory lining, a hermetically sealed receptacle mounted adjacent said vessel for feeding material into said vessel,

means dividing said receptacle into a main compartment and a plurality of auxiliary compartments, said auxiliary compartments being volumetrically inter-related according to a geometric progression which increases by a factor of two, valve means for connecting said main compartment to said vessel and an independently operable valve means disposed between each of said auxiliary compartments and said main compartment so that the contents of said auxiliary compartment may be selectively discharged into said main compartment.

5. A vacuum vessel for vacuum treating a ladle of molten metal disposed therebelow, said vessel having a metallic shell and a refractory lining, a nozzle extending from the lower end of said vessel and opening into the interior of said lining, means for producing relative movement between said vessel and said ladle to dip the lower end of said nozzle into said molten metal so that said vessel and the said molten metal defines a hermetically sealed chamber, means for producing a partial vacuum within said chamber, a hermetically sealed hopper mounted on said vessel and in communication with said chamber, mean dividing said hopper into a main compartment and a series of trimming compartments, said trimming compartments being volumetrically related according to a geometric progression wherein each succeedingly larger trimming compartment has a volume which is twice as large as the compartment preceding it in said progression and means for selectively discharging predetermined ones of said trimming compartments into said main compartment.

References Cited by the Examiner UNITED STATES PATENTS 177,267 5/76 Muller 222-430 X 543,423 7/95 Guthrie 222430 805,290 11/05 Henzel 222430 X 1,615,438 1/27 Bott 141104 X 2,289,807 7/42 Schaevitz et al. 221-426 2,760,653 8/56 May 214-1762 X 2,788,270 4/57 Nisbet et al. 26634 2,790,493 4/57 Wenzelberger 21317 X 2,858,125 10/58 Clenny et a1 26634 2,891,782 6/59 Blackman et al 26634 2,895,820 7/59 Harders 26634 2,940,620 6/60 Haas 214--18 FOREIGN PATENTS 1,224,375 2/ France.

MORRIS O. WOLK, Primary Examiner.

RAY K. WINDHAM, Examiner. 

1. IN COMBINATION, A SEALED VESSEL FOR THE VACUUM TREATMENT OF MOLTEN METAL, AND HERMETICALLY SEALED RECEPTABLE MEANS MOUNTED ADJACENT SAID VESSEL AND INTERCONNECTED THERETO, SAID RECEPTACLE MEANS BEING DIVIDED INTO A PLURALITY OF COMPARTMENTS COMPRISING A MAIN COMPARTMENT AND A PLURALITY OF AUXILIARY COMPARTMENTS, SAID AUXILIARY COMPARTMENTS BEING VOLUMETRICALLY INTER-RELATED ACCORDING TO A GEOMETRIC PROGRESSION WHICH INCREASES BY A FACTOR OF TWO FIRST MEANS FOR INDIVIDUALLY DISCHARGING THE CONTENTS OF SAID AUXILIARY COMPARTMENTS INTO SAID MAIN COMPARTMENT AND SECOND MEANS FOR DISCHARGING THE CONTENTS OF SAID MAIN COMPARTMENTS INTO SAID VESSEL. 